Well, apparently you can't (I think I saw a post to that effect earlier).
Mind you that I am but 56 years old and that the meaning of words and sayings do change over time, but I am pretty sure, in my admittedly limited experience with life and women, that "having sex" still means something other than just/only penetration.
If you do believe that "having sex" is only about penetration then I weep for the women with whom you are involved, and then it is a clear and resounding: NO.
If, however, you believe that "having sex" is so much more than simple penetration, then you are indeed in luck with 0.8., meaning that Mary and mc do indeed get to spend some quality time together.
Be certain that 0.9 will start you off with a "bang", if you have chosen Mary.
Cheers - Kaffekop